Integrative impacts of salicylic acid and water deficit stress on physiological processes of medicinal herb Bacopa monnieri (L.)

Rapid environmental fluctuations, particularly water deficit stress, significantly hinder a plant’s growth by constraining primary metabolic processes. Salicylic acid (SA), a recognized plant hormone, exhibits a noteworthy role in alleviating water stress impacts on leaf gas exchange. This study investigates the interaction between SA and water deficit (WD) stress in Bacopa monnieri (L.). Different SA doses (50, 75, 100, and 125 mg/l) were foliar-sprayed, with water deficit imposed by reduced irrigation (well-watered, water deficit 1, and water deficit 2). Pooled data from 2 years indicated increased electrolyte leakage and decreased photosynthetic pigments, photosynthesis rate, and protein content in WD2-stressed plants. Moderate SA concentrations with WD1 and WD2 stress positively impacted photosynthesis-related traits and enhanced defense mechanisms, reflected in increased total protein, leaf water potential, and chlorophyll stability index. Positive correlations between photosynthesis rate and antioxidants suggests SA’s role in fortifying plant defense mechanisms against stress. Overall, this research underscores SA’s resilient role in mitigating water deficit stress effects by regulating various physiological and metabolic processes, ultimately supporting plant growth.